Digital network communication systems enable telecommunication service providers to supply multiple types of information channels from a sourcing site, such as a central office, to a network termination interface at a remote site serving a number of customer premises equipments (CPEs). A reduced complexity example of such a digital communication network architecture is diagrammatically illustrated in FIG. 1 as comprising a TDM communication link (such as an optical fiber) 10, through which a central office (CO) 20 at a `west` end of the TDM link 10 transmits and receives digital telecommunication (e.g., T1 (1.544 Mb/s)) traffic with respect to customer premises equipments served by a remote termination site 30 at an `east` end of the PCM link 10. The central office 20 may include a central office switch 21 (such as a 5ESS switch manufactured by AT&T), that contains a plurality of line terminations 22, each of which is coupled over digital facilities and distributed onto a local loop (twisted tip/ring pair) to a respective local DS0 customer site.
As shown in FIG. 2, to provide telecommunication service to remote customer equipments, the equipment shelf of a remote terminal 30 terminating the `east` end of the PCM link 10 contains a network interface unit (NIU) 31, that is coupled over an internal bus or backplane 32 to a plurality of circuit cards 33 installed in the interface unit's backplane 34. Historically, each circuit card 33 was dedicated to providing telecommunication service for a particular piece of remote customer premises equipment, via a local loop 35 between the circuit 33 card and DS0 digital communication equipment 37 installed at a respective customer premises.
However, with improvements in integration circuit density and signal processing speed, digital telecommunication circuit manufacturers now offer a variety of multiple port devices having a wide range of operational bandwidth and digital subscriber line termination capabilities. Now although these enhanced bandwidth capability devices can transport a substantially increased amount of information, and/or enable a single card to service a relatively large number of terminating devices, their diverse configurations have required that transport connectivity among devices be effected by means of point-to-point communication links, which prevents their integration into an equipment shelf having a distributed backplane architecture.